How long on meds for 1 seizure?

My son had one seizure at age 18, after a stressful time his senior year and being sick with strep. He had an abnormal EEG a week after the seizure so the neurologist put him on Keppra. He became severely depressed so the neurologist switched him to lamotrigine. He was doing OK for a few months, but now after about a year on 250mg lamotrigine xr the depression is coming back along with concentration issues. He was always a very good student but since taking these meds his grades have been suffering. He is so depressed on lamotrigine right now but the neurologist says it's a mood stabilizer and can't be causing the depression? I don't agree, it states on the medications that a side effect can be depression.. We were sent for a neuropsychological exam to determine what might be causing the depression. It will take weeks to get the results. All the while, no changes have been made and he is still suffering from depression. He has not had a seizure in over 2 years, and I'm wondering how long he needs to be on medication. Is it reasonable to go off meds after 2 years of being seizure free? He just had a 24 hr EEG which was normal, but that was on lamotrigine. Can seizures be controlled with lifestyle changes such as getting enough sleep, exercise, eating healthy? If staying on meds in necessary, what meds do not cause depression, anxiety, anger, etc..? I am desperate to see my son's normal personality come back, this is terrible and ruining his college years. Any advice would be very much appreciated, we go back to the doctor soon.